We propose to extend our mechanistic studies in the prenyltransfearase reaction by defining the mechanism of termination of the polymerization reaction. In addition, we will utilize a mixed prenyltransferase to further elucidate the role of metal ions in this reaction. Mechanistic studies involving fluorine analogues and isotope effects are projected for prenylisomerase. A careful enzymological study of this enzyme will also be necessary. A continued examination of the branch points of terpene biosynthesis and regulation thereof in eucaryotic cells is also proposed.